The present invention generally relates to apparatus for controlling heating and ventilating equipment, and more particularly for controlling heating and ventilating units and associated equipment that are often used in individual rooms of schools and the like, often referred to in the art as unit ventilators.
In the art of heating, ventilating and air conditioning (HVAC) for buildings and the like there has been a continuing effort in developing more accurate and sophisticated controls for accurately controlling the systems to provide more accurate control in terms of maintaining the desired temperature within a space, and minimizing the energy required to provide heating and/or air conditioning, and in providing increased safety. With the increased utilization of computers, such systems can now be controlled by what had been considered to be complex control schemes that had been used in only very expensive, sophisticated supervisory and control systems. In many of such systems, pneumatic pressure control lines extended between components of the system for controlling the operation of the system. The use of such pneumatic lines has existed for decades and systems using the same continue to be installed. As a result of the long use of such pneumatic control lines, there are thousands of systems in existence which are desirable targets for upgrading in the sense that more sophisticated control may be desirable from a cost benefit analysis, given the relatively inexpensive and robust technical capabilities of control systems compared to the seemingly ever increasing cost of energy for providing heating and air conditioning.
Apart from these general considerations, there are many buildings that exist which often are heated in the winter, but because they have little usage in the summer months and other reasons, true air conditioning is not provided in them. A prime example is that of school buildings which have many classrooms that are heated by individual heating units, which are commonly known as unit ventilators. Such unit ventilators are generally connected to a heating plant that communicates heat to the ventilators via a heated fluid, such as hot water or steam lines, although electrical heating elements are sometimes employed.
With the unit ventilators being located in each room, many older unit ventilators are not conducive to being controlled by a single supervisory and control system, except to the extent that the pneumatic control lines can be switched between nominal pressure values which reflect differing set points for day or night operation and the pneumatic lines can be controlled from a common pressure source. Pressure detectors in the unit ventilators are adapted to sense the difference between the day/night nominal pressures and therefore provide some degree of control, albeit not overly sophisticated. The temperature control of the rooms is provided by a pneumatic thermostat located within the room at some distance from the unit ventilator so that it provides a fair reading of the temperature of the room rather than the discharge temperature of the air that flows from the unit ventilator.
Unit ventilators generally have a damper for controlling the admission of air from outside the room, and also typically employ a fan which forces air through the ventilator which obviously includes heating coils.
Accordingly, it is a primary object of the present invention to provide an improved controller for use with unit ventilators of the type described above.
A related object is to provide such an improved controller which incorporates a processing means and is therefore adapted to utilize relatively complex and sophisticated control schemes in the operation of the controller.
Another related object lies in the provision for interconnecting the unit ventilator controllers with a remote control means so that centralized operation of many unit ventilators in a building or the like can be performed.
Still another object of the present invention is to provide a controller for existing unit ventilators which employ pneumatic control lines, with the controller providing a controlled pressure in one or more pneumatic lines that are used to control pneumatic valves that regulate the position of the outside air damper as well as modulate the flow of heating fluid to the heating coils of the unit ventilator.
Yet another object lies in the provision of providing day or night modes of operation, heating or cooling modes of operation, with each mode having different temperature set points that can be independently determined. An ancillary object lies in the provision for setting the various set points from the remote controller location.
Still another object lies in the provision for enabling or disabling the room thermostat set point control, so that a room set point may be determined from the remote controller means location rather than by an individual in the room itself.
Another object of the present invention is to provide such an improved controller for unit ventilators which utilizes control schemes and input parameters that include signals that are generated that are indicative of the pneumatic output line control pressure, the room temperature, the temperature of the air immediately downstream of the heating coils, i.e., the discharge temperature of the unit.
Still another object of the present invention is to provide such an improved controller for unit ventilators which is modular and compact in its construction, is easily installed in existing unit ventilators and provides not only the controlled pneumatic pressure in the output lines for the controller, but also provides electrical control signals for controlling the operation of the fan.
Yet another object of the present invention is to provide such an improved controller for unit ventilators which include processing means having associated memory that provides extreme flexibility in the operation of the control of the unit ventilator in the sense that control schemes may be provided and changed to employ any desired control algorithm that may beneficially operate the controller, provided that the size of the algorithm is consistent with the memory size.